Geological characteristics and potential of geothermal resources in the uplift mountain-type of Hainan Island

Objective Hainan Island is very rich in geothermal resources of the uplifted mountain−type, with 46 geothermal fields and hot springs discovered. Studying the geological background, geothermal geological characteristics, genesis, and resource potential is of great significance for understanding the occurrence regularity, exploration, and development of geothermal resources.

Methods Based on comprehensive regional geological surveys, geophysics, hydrogeological, regional geological surveys and geothermal fields (hot springs) survey data, to carry out a comprehensive study on geothermal geology of the uplifted mountain−type geothermal resources in Hainan Island . a systematic analysis of geothermal geological elements, basically clear the geothermal geological characteristics, genetic model, and the potential of the resources, pointed out a favorable area for geothermal resource exploration and development.

Results Geothermal fields (hot springs) in the south−central uplifted mountainous−type of Hainan Island.are mainly located in the east−west and north−east near the deep−seated faults or the intersection of fractures, in the high value of the heat flow and high anomalies of constant temperature layer, broken by the fracture of the Mesozoic granite is the most important heat storage. Geothermal fields (hot springs) groundwater recharge are atmospheric precipitation, along the heat−controlled fractures and deep earth heat flow convection, heat absorption in the deep cycle process gradually formed geothermal fluid, in the fracture zone thermal storage for the enrichment of thermal mineral water body, in the cover of the weak drainage out of the surface is the formation of hot water springs. Hainan Island uplifted mountain−type geothermal resources, the total amount of recoverable thermal water of about 8.1×10⁴ m³/d, the recoverable resources 26.17×10⁸ kcal/d, equivalent to 126.81 MW, equivalent to the standard coal of 373.83 t/d, according to the temperature of the geothermal resources and the scale of classification, respectively, are divided into medium−temperature, low−temperature and medium−scale, small−scale geothermal resources.

Conclusions The areas near or at the intersection of deep−seated faults in the southeast and northwest of Hainan Island, the high value area of geothermal heat flow, the exposed (or hidden) area of Mesozoic granite intrusion, and the areas with high surface water temperature are favorable areas for exploration and development of uplifted mountain−type geothermal resources.